Image Of Test Pattern Research Articles

Scanning coherent diffractive imaging methods for actinic extreme ultraviolet mask metrology

For the successful implementation of extreme ultraviolet (EUV) lithography in the upcoming technology nodes, a major challenge to overcome is the stable and reliable detection and characterization of mask defects. We have recently presented a reflective mode EUV mask scanning lensless imaging tool (RESCAN) which was installed at the XIL-II beamline of the swiss light source and showed reconstructed aerial images of test patterns on EUV masks. RESCAN uses scanning coherent diffractive imaging (SCDI) methods to obtain actinic aerial images of EUV photomasks and was designed for 80 nm onmask resolution. Our SCDI algorithm reconstructs the measured sample by iteratively solving the phase problem using overdetermined diffraction data gathered by scanning across the specimen with a finite illumination. It provides the phase and amplitude aerial images of EUV photomasks with high resolution without the need to use high numerical aperture (NA) lenses. Contrary to scanning microscopy and full-field microscopy, where the resolution is limited by the spot size or NA of the lens, the achievable resolution with our method depends on the detector noise and NA of the detector. To increase the resolution of our tool, we upgraded RESCAN with a detector and algorithms. Here, we present the results obtained with the tool that is capable of up to 40-nm onmask resolution. We believe that the realization of our prototype marks a significant step toward overcoming the limitations imposed by methods relying on imaging optics and shows a viable solution for actinic mask metrology.

Stopping criterion for anisotropic image diffusion

Coherence-enhancing diffusion filtering is a striking application of the anisotropic diffusion in image processing. The technique deals with the problem of completion of interrupted lines and enhancement of flow-like features in fingerprint images. However, an anisotropic diffusion process is an iterated process, initializes with a poor quality image, and converges at the end towards a completely blurred image, with no structure surviving at the end. In anisotropic diffusion, one important question is how to find boundary between the under-smoothing and over-smoothing regions of the anisotropic diffusion process. The entropy change is found to be one such measure to describe that boundary adequately and thus provides a reasonable stopping rule for anisotropic diffusion. Numerical experiments with test pattern images confirm the desirable qualities of gap-closing and flow-enhancing qualities, along with the identification of frontier of useful smoothing. The proposed scheme is evaluated with the help of simulated images, and compared with other state of the art schemes using an objective criterion.

Unsupervised Neural Network Quantifies the Cost of Visual Information Processing.

Untrained, “flower-naïve” bumblebees display behavioural preferences when presented with visual properties such as colour, symmetry, spatial frequency and others. Two unsupervised neural networks were implemented to understand the extent to which these models capture elements of bumblebees’ unlearned visual preferences towards flower-like visual properties. The computational models, which are variants of Independent Component Analysis and Feature-Extracting Bidirectional Associative Memory, use images of test-patterns that are identical to ones used in behavioural studies. Each model works by decomposing images of floral patterns into meaningful underlying factors. We reconstruct the original floral image using the components and compare the quality of the reconstructed image to the original image. Independent Component Analysis matches behavioural results substantially better across several visual properties. These results are interpreted to support a hypothesis that the temporal and energetic costs of information processing by pollinators served as a selective pressure on floral displays: flowers adapted to pollinators’ cognitive constraints.

Demonstrating 30-nm spatial resolution of three-multilayer-mirror objective for extreme ultraviolet microscopy: Imaging test by observing lithography mask

To confirm the high spatial resolution expected in extreme ultraviolet (EUV) microscopy, fine grating patterns with a half-pitch of less than 100 nm on a lithography mask were imaged using a full-field microscope based on a multilayer-mirror objective. When the tilted illumination technique is applied to this novel imaging system, a spatial resolution better than 20 nm can be expected at a wavelength of 13.5 nm. We demonstrated high resolution via EUV reflection images of test patterns with a half-pitch between 30 and 80 nm.

Experimental and modeling studies of imaging with curvilinear electronic eye cameras

Model calculations and the experimental measurements of the imaging properties of planar, hemispherical, and elliptic parabolic electronic eye cameras are compared. Numerical methods for comprehensive full field calculations of image formation are enabled by use computationally efficient modes. Quantitative agreement between these calculations and experimentally measured images of test patterns reveals advantages of curvilinear camera systems, and provides guidelines for future designs.

Optical Coherence Tomography用合成光源の基礎研究

We have studied on the light intensity ratio of synthesized light source (SLS) for the improvement of spatial resolution of optical coherence tomography (OCT). SLS consists of two LEDs with wavelength 691 nm, spectral width 99 nm and 882 nm, 76 nm. The small imaging interferometer also consists of plan-convex lens of focal length 6 mm and diameter 6 mm, beam splitter and reference mirror with PZT. The axial resolution was measured at 1.2 μm with the side lobe intensity 42 % on the condition of intensity ratio of 1:0.5. The irradiated power was 18 μW. This axial resolution was 57 % compared to the axial resolution using a single LED. The image of test pattern was measured using the phase shift method and two lines with the interval of 9.8 μm were clearly measured. The lateral resolution was calculated at 1.1 μm from wavelength and numerical aperture.

Image Quality of Digital Photography Prints—II: Dependence of Print Quality on Pixel Condition of Input Camera

In digital photography, input photoimages to the electronic camera are sampled by segmental imager and converted into image data. The smallest unit of division is called a pixel and the segmentation fixes the size and number of those pixels. Output picture definition is directly related to the pixel number of the input imager. Moreover the image processing to modify the pixel condition influenced the tonal quality of output image. This article discusses the relationship between the conditions of pixel in the imager of the input digital still cameras (DSC) and the image quality of output prints in a digital photography system. Sample color prints showing the same test pattern images in different definition proportional to the numbers of pixel were produced by a single digital photography system. The correlation between the pixel condition of input device and the structural and tonal image quality of output prints were apparent to the subjective visual examination and the objective physical analyses. The effects of pixel condition appeared in the drastic MTF changes on the image structure and the apparent definition changes on the tone rendition of reproductions on the sample prints. The results suggest that there is a limiting pixel number for digital cameras to produce satisfactory hand-held size digital photography color prints.

A low-temperature scanning confocal and near-field optical microscope

A scanning near-field optical microscope equipped with an Al-coated glass fiber tip for operation in a He cryostat is described. The instrument is designed for fluorescence detection of nanoscopic particles (single dye molecules and nanocrystallites), and allows optical imaging and spectroscopy of surfaces or thin objects with subwavelength spatial resolution at low temperatures. A shear-force control loop keeps the probing fiber tip aperture at a constant distance, i.e., a few nanometers away from the sample. The shear-force method results in a vertical stability of better than 2 nm. For light collection and confocal imaging, a transmission objective with a high numerical aperture is operated inside the cryostat. For rapid sample inspection, and in cases where no high lateral resolution or topographic imaging is necessary, the instrument can also be used without a tip as a low-temperature conventional or confocal microscope, due to the large scan range of an improved scanner. Details and characteristics of the experimental setup as well as first results are presented. First shear-force images of test patterns taken at low temperatures down to T=22 K, as well as near-field optical fluorescence images of low concentrated sulforhodamine molecules dispersed in a thin polymer film at T=75 K and room temperature, are shown. With this instrument, confocal images of CdS nanocrystallites were taken at 20 K.

Effect of x-ray tube motion on dental radiographic resolution

X-ray tube movement during intraoral radiography is generally discouraged; however, the effects have not been quantified or reported. A portable x-ray tube head was mounted on the horizontal cross-beam of Instron model 1125 universal testing machine. Precise movement from 0 to 25 mm of oscillation was accomplished in increments of 1 mm. Four test objects were imaged during x-, y-, and z-axis movement of the tube head. Pinhole camera and star test pattern images were used to measure focal spot size for each increment of motion. Images of a resolution plate and a section of dry mandible were used to evaluate levels of resolution objectively and subjectively for each increment of motion. Results indicate that the size of the effective focal spot increases predictably with increasing increments of tube motion accompanied by a corresponding loss of resolution. Movement of the tube along the x- and y-axis relative to the plane of the film produced similar losses of resolution and were much greater than loss associated with z-axis movement.

Intra-arterial DSA: early experience with a 1024(2) matrix.

Twenty patients were studied with intra-arterial digital subtraction angiography (IA DSA), utilizing a 1024(2) matrix memory. Acquisition of the images was through a prototype television camera incorporating a finely focused electron beam. In five cases, comparison between a 512 X 512 (512(2)) matrix acquisition and a 1024 X 1024 (1024(2)) matrix acquisition mode was made, with injections occurring in the same vessel in the same patient. The clinical material demonstrated no significant improvement in image quality at the 4 1/2 as well as the 6 inch image intensifier (II) modes. However, the 1024(2) matrix combined with the 9 inch II mode showed foci of disease and normal anatomy with detail not always seen on the 9 inch II when a 512(2) matrix was used. In no case, however, was the basic diagnosis missed with the 512(2) matrix. Spatial resolution, as measured from lead bar test pattern images, demonstrated that the 1024(2) matrix allows a 70% or greater improvement in spatial resolution over the 512(2) for the 4 1/2, 6 and 9 inch II modes. For a given mode the radiation dose was held constant for the two matrix sizes.

Influence of Defocussing on Retinal Images of Test Patterns Calculated with the Modulation Transfer Function

The modulation transfer function (MTF) of the frog’s eye was used to calculate retinal intensity distributions of several test patterns. The state of refraction was varied between ––14 D and + 8 D, and the influence of defocussing was studied. Conclusions: (1) The optical resolving power of the eye depends on the type of the stimulus. (2) The criterion that is used (maximum amplitude or half-width) results in different values of resolving power for points and lines. (3) The retinal image of the double line and the double point has a threshold characteristic. Below a certain threshold there is no modulation of the image, and the separation of the maxima of the image is zero. (4) Defocussing in the positive direction (i.e., when the refractive power of the eye and the auxiliary lens is too high) degrades the image more than an equal negative refractive error. (5) The double line is a more suitable stimulus for accommodation than the double point.